Reflector lamps need to accommodate both beam spread and beam esthetics. Commonly, the user seeks a beam with a spread angle that fits a particular need. Beams are basically formed by the reflector contour. Typically a parabola of rotation is used to provide a tightly collimated, parallel beam. A perfectly smooth reflector however projects images of the underlying light source. The filament or arc image is then seen as a light pattern projected onto the object being lit. This undesirable result is usually overcome with lenticules on the lens that break up the source image. Lenticules are also used to spread the light, for example from a parallel beam to a cone with a chosen spread angle. Lenticules are commonly arranged in patterns, but they can form overlapping light patterns that result in streaks of light or dark. For example, a typical hexagonally closed packed lenticule pattern results in a hexagonal beam pattern as shown in FIG. 1 (video scanned image). Such patterns may be acceptable for lighting a driveway, but it is objectionable in consumer displays, or similar applications where esthetics are important. In general, source image dispersion leads to a more diffuse spot, and less light on the subject area. There is then a need for a PAR lamp with a well defined spot, and a dispersed source image.
Beam esthetics are difficult to define. This is due to the active response of the human eye and brain to integrate the actual light pattern into a perceived pattern. The perception process depends in part on the color, intensity, contrast and other of factors of the actual light in the beam, and also on how much stray light exists outside the perceived beam. Beam esthetics can be affected by such variables as focus of the light source in the reflector, defects on the lenticules and the characteristics of visual perception. The human eye, for example, acts to enhance edges for contrast, so when presented with a sharp change in light intensity, the perceived beam edge is enhanced. This process unfortunately can enhance beam defects that may appear insignificant when measured with a meter. This process also results in optical illusions. For example in a beam with a sharp cut off, there can be a perception of a bright beam center surrounded by an even brighter ring that is surrounded in turn by a dark ring surrounded by a less dark exterior region. The bright ring and the dark ring are illusory, and cannot be identified with actual meter readings. The collimated light of a PAR lamp not only produces sharp cutoffs when spread through a spherical lenticule, it can also show manufacturing defects that can occur in the lenticule. Any structured deviation from the spherical contour can be visible in the beam if a parabolic reflector is used. There is then a need for a reflector lamp with good beam spread, a well defined spot that is evenly lit with good diffusion of source images, and little or no illusory image effects.